Microfiltration, ultra filtration, and reverse osmosis all involve the physical separation particulate matter from a fluid. In general, particulate contaminants may be removed by mechanical filtration methods, provided the filter has pores small enough to exclude the particles. Substances that are larger than the pores in membranes are fully removed. Substances that are smaller than the pores of the membranes are partially removed, depending on the structure or construction of a refuse or filtrate layer on the membrane.
In the case of water purification (e.g., industrial, municipal, and/or residential water purification), the extent to which dissolved solids, turbidity, microorganisms, and ions are removed is determined by the size of the pores in the membranes. FIG. 7 provides a scale of various pore sizes and/or size ranges along with the types of materials (e.g., particulate matter) that can be filtered from a fluid by a filter membrane having the identified pore sizes. Microfiltration utilizes membranes with a pore size of 0.1 to 10 microns, which can remove virtually all bacteria from the water to be filtered. Ultra-filtration (UF) membranes typically have pore sizes in the range of 0.01 to 0.10 microns and can efficiently remove bacteria and most viruses, colloids (e.g., lead), and silt.
Separation efficiency is increased with filters containing smaller pore sizes, although higher pressures are needed to maintain flow through the filter. Thus, a filter having a smaller pore size requires a high-pressure pump or other means of creating high pressure. Such equipment typically requires and consumes a relatively large amount of energy to carry out the filtration process, and may require relatively complex and/or costly techniques to clean the filters.
A method commonly used to separate solids from liquids includes passing a mixture of solids and liquids through a tubular membrane or filter. Such filters are typically used, for example, in reverse osmosis processes. Such separation processes require high fluid pressures to push the liquid through the filter and separate the liquid from contaminants. Typically, the high fluid pressure is achieved by using a high-pressure pump. These high-pressure pumps consume large amount of energy in creating adequate filtration pressures, especially as the amount of particulate matter blocking the pores increases. There is a continuing need for more energy-efficient fluid filtration systems.
Centrifuges and other machines that use centrifugal force (and optionally, a filter) to separate fluid components from solid-phase materials (e.g., a washing machine) provide energy efficiencies with regard to the inertia created by the spin of the drum or rotor around a central drive shaft. There are known centrifugal filtration systems (e.g., a household washing machine) for separating liquids (water) from solids (fabric/clothing). However, application of this type of apparatus to perform other tasks such as wastewater treatment, recycling industrial solvents, pharmaceutical and blood product purification, and water purification in food product industries encounter several technical difficulties and limitations. For example, practical applications of a centrifugal system for separating particulate contaminants from water in waste water treatment are generally limited by the filter(s) and their suitability for separating certain types of particulate matter (e.g., the holes may be too large to separate most of the suspended solids in the waste water).
Therefore, a need still exists in the art for new and improved systems, configurations and operational processes that can separate particulate matter from relatively high volumes of fluid or gas with greater efficiency, scalability, and ease of cleaning.